1. Field of the Invention
The present invention relates to an endoscope, and more particularly, to an assembling method for coupling optical fiber bundles of an endoscope, such as an image guide and a light guide, to a distal end member and a control section.
2. Description of the Related Art
In a typical conventional endoscope, optical fiber bundles, such as an image guide and a light guide, are passed between a control section and a distal end member of an insertion section, which, extending from the control section, is adapted to be inserted into the body cavity or the like. The image guide is optically coupled to an eyepiece portion at the control section and an objective lens mounted on the distal end member. The light guide optically connects a light source connector, which is attached to a universal cord connected to the control section, and an illumination window attached to the distal end member.
In general, the opposite end portions of one such optical fiber bundle are fixed individually to the control section and the distal end member by means of screws or other mechanical means. A specific arrangement of such fixing means is stated in Japanese Patent Disclosure No. 61-245120, for example. The end portions of the optical fiber bundle are constructed so that simple glass fibers are compacted by means of a bonding agent or the like. Since the mechanical strength of the compacted end portions are very low, reinforcement metal pipes are put individually on the end portions. One of the pipes is fitted in an insertion hole formed in the distal end member, and is fixed to the end member by means of screws.
Conventionally, the aforementioned structure is assembled in the following manner. First, the reinforcement pipes are fitted individually on the end portions of the optical fiber bundle, outside the endoscope. Then, the fiber bundle is passed through the insertion section between the control section and the distal end member. Thereafter, the reinforcement metal pipes at the opposite end portions are fixed individually to the control section and the distal end member.
According to the assembling method described above, however, the optical fiber bundle is previously fitted with the reinforcement pipes, on its end portions, before it is passed through the insertion section. Accordingly, the diameter of the end portions to be inserted is so large that the fiber bundle cannot be easily passed. More specifically, the insertion section of the endoscope is a bendable structure including a bending portion, which is composed of a number of tubular segments rockably coupled to one another. The bending portion houses optical fiber bundles, including an image guide, light guide, etc., forceps channel, gas/liquid feed tube and the like. Accordingly, the bending portion hardly has any inside space through which the optical fiber bundles are to be passed. When an optical fiber bundle with a thick reinforcement metal pipe thereon is passed through the bending portion, therefore, the pipe tends to touch the forceps channel, gas/liquid feed tube, etc. Thus, if the metal pipe is forced into the bending portion, the touched elements may possibly be damaged.
If the metal pipe on the end portion of the optical fiber bundle is reduced in size, therefore, its wall-thickness is also reduced. Thereupon, the mechanical strength of the metal pipe is lowered, so that the pipe may possibly be deformed when it is fixed by means of the screws. If the metal pipe is deformed, then the end portion of the optical fiber bundle will be distorted.
Thus, there is a demand for the development of an improved assembling method for an endoscope in which the optical fiber bundle can be easily passed through the bending portion, and the metal pipes can be fitted on the end portions of the fiber bundle without the consideration of their outside diameter.